French scientists from Aix-Marseille University found that mice's facial expressions can reflect not only emotions, but also the course of thought processes. Neuroscientists observed rodents as they chose between water dispensers with changing probabilities of reward. The mice's behavior was recorded on video at 60 frames per second.
An analysis of more than 14,000 decisions showed that tiny facial movements — especially around the nose and whiskers — contain information about the strategies under consideration, even if those strategies were not chosen. This is confirmed by comparing the data with neural activity in three brain regions, including the orbitofrontal cortex and the supplementary motor cortex. In some cases, changes in facial expression preceded neural signals by tens of milliseconds.
This discovery is important not only for understanding animal behavior, but also for medicine. The ability to “read” internal brain states from video images — without implanting sensors — opens up prospects for diagnosing psychiatric and neurodegenerative diseases. This is especially relevant where traditional tests are not very informative: in children, older adults, or people with speech impairments.
